There are two ways you can use the pulgar (thumb). The first is when the movement originates from the main joint where your thumb is attached to your hand also known as the "trapezio-metacarpal joint." With this technique, you play passages that incorporate both the thumb and the fingers together, such as arpeggios, tremolo, or any other bits that have active and interwoven bass and treble sequences. The free stroke exercise video I posted for my earlier blog entry is a good example for that. The wrist stays as steady as possible while the thumb and the fingers move somewhat independently from each other.

The other pulgar technique is the one where the movement comes from the wrist. Actually, to be precise, the movement originates from "proximal radio-ulnar joint" at the elbow. Your forearm twists a bit to give your whole hand/wrist a radial movement. You keep your thumb as straight and steady as possible and pound on the strings by slightly rotating your wrist. This technique is used quite a bit in flamenco. It generates that loud, buzzy flamenco sound. For students trying to familiarize themselves with the flamenco pulgar, I suggest practising short scales by tucking the index finger underneath your thumb as if holding a pick. This will lock your thumb in position and ensure the movement and the main force come from the wrist. Once you've gotten accustomed to the basic movement, you don't have to squeeze your thumb and index finger together; do this if you are completely unfamiliar with the technique.